Passengers dinged for overweight bags this holiday season won't be able to blame the scale if they're flying US Airways or Southwest out of Phoenix.

The Arizona Department of Weights and Measures, responding to a recent complaint by a US Airways passenger, did a surprise inspection of the airlines' scales at Sky Harbor International Airport on Friday.

A team of inspectors tagged 31 of the 72 scales with infractions, but all but three were minor and none was to the airline's advantage.

"We're not finding any real egregious problems," said Steve Meissner, spokesman for the agency.

Southwest, which has nearly 200 daily flights from Phoenix, had to shut down three of its 26 scales because they received red tags, the most serious violation, from the inspectors. The problem: The scales did not start at zero.

In Southwest's case, they started before zero, so any error would be in the customer's favor. But Meissner said a faulty scale can just as easily go the other way, so it has to be fixed before it can be used again.

"An inaccurate scale is an inaccurate scale,'" he said.

Southwest had three other machines with more minor violations, such as a digital readout that doesn't work, so they received a yellow tag.

A Southwest spokeswoman said the airline called in a technician immediately and expected to have the three problem scales back in use by Friday night.

Tempe-based US Airways, the busiest carrier at Sky Harbor with nearly 300 daily flights, had 46 scales inspected and 25 received yellow tags. A spokeswoman said the carrier has its scales calibrated once a month, and the next one was due to occur on Saturday. US Airways and Southwest, both based in Terminal 4, are Sky Harbor's dominant carriers, accounting for more than three-fourths of the passenger traffic.

The accuracy of the scales is a money matter for passengers.

Airlines charge a fee for bags more than 50 pounds and have been enforcing the policy more than ever. Passengers can either pay up or stuff the extra weight into a lighter bag to balance things out.

US Airways charges between $50 and $100 per overweight bag each way; Southwest, $25 to $50.

In US Airways' case, those fees are in addition to new fees to check a bag.

"This is important to do," Meissner said. "It's the holiday season and we're about accuracy."

The weights and measures department aims to inspect airport scales once or twice a year but has been behind because of an increase in inspections of gasoline pumps.

Complaints in that category more than tripled as gas prices spiked, Meissner said.

"Airport scales take a lot of use and, frankly, a lot of abuse," he said. "People walk on them. They dump heavy things on them ... They need a lot of maintenance."

The agency plans to inspect scales at terminals 2 and 3 but does not have a timetable, Meissner said.

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